textproduct: Quad Cities

KEY MESSAGES

- Active weather is likely midweek as a storm system brings along the chance (60-80%) for heavy rainfall and a low-end severe threat. There is higher confidence on localized flash flooding.

- Seasonal temperatures will remain through the week with temperatures and humidity on the rise this weekend.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 120 AM CDT Tue Aug 4 2026

Dry, seasonable conditions continue through this afternoon before a cold front moves into the area from the northwest supported by a longwave trough over the Northern Plains. Mean southwesterly flow in the 1000mb-500 mb layer will advect in moisture as PWATs soar to 1.5-2 inches areawide by this evening. Scattered showers and storms (20-40% coverage) could reach areas north of Highway 30 in Iowa by the early afternoon before increasing in coverage into the evening and overnight hours and spreading southeast. Along the front, SBCAPE values are likely (70-90% chance) to exceed 1000 J/kg with 20-30 knots of 0-6 km bulk shear. There is a low probability (less than 5%) for these afternoon storms to turn severe, but localized gusty winds and heavy downpours cannot be ruled out.

The cold front clears most of the CWA tonight before stalling across Illinois and central Missouri. This will not be the end of precipitation though as an elevated F-gen band in the 850mb- 700mb layer is forecast to generate numerous post-frontal showers and storms (60-80% coverage) despite a surface high pressure moving in. The severe threat with these storms should diminish north of Interstate 80 as surface CAA kicks in behind the front, but areas along and south of Interstate 80 retain a Marginal Risk (Level 1 of 5) for severe storms on Wednesday due to their proximity to the boundary and elevated instability. Regardless, the primary hazard late tonight into Wednesday is flash flooding with the potential for repeated rounds of heavy rainfall on top of already saturated grounds from last weekend. Current REFS guidance has areas south of Interstate 80 with a 60-90% chance of exceeding 1 inch of rainfall while areas north only have a 20-50% chance. Regardless, there will likely be swaths of 2+ inches, and this is why the WPC has a Slight Risk (Level 2 out of 4) for excessive rainfall areawide.

Heading into Wednesday night, another shortwave swings into the base of the longwave trough now over the Upper Mississippi River Valley, allowing for another pulse of showers and storms (40-70% coverage) to affect areas along and south of Highway 30. This shortwave will also pull a low pressure system over the Southern Plains to the northeast along the stationary boundary south of Highway 34, keeping PoPs around into Thursday.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 120 AM CDT Tue Aug 4 2026

Thursday-Friday...The surface low reaches central Missouri during the day Thursday as enhanced diffluent flow aloft supports the isolated showers and storms (20-30% coverage), mainly south of Interstate 80. By Thursday night, another shortwave trough dives in from the northwest, but dry air advection is expected to suppress precipitation. By Friday morning, ageostrophic convergence aloft on the backside of the longwave trough now over the Great Lakes should lead to a mostly dry Friday. This will be short-lived though as another surface trough moves into the Northern Plains Friday night.

Saturday-Monday...Low PoPs (20-30%) remain on the table heading into the weekend and early next week as continual longwave troughing over Hudson Bay and northwesterly flow aloft over the region may allow for multiple weak shortwave and surface boundary passages. A warming trend appears more likely though as southerly flow ahead of these fronts advect in warm and moist air. Highs along and south of Highway 34 are likely (60-80% chance per 03.12z LREF guidance) to climb back into low 90s Sunday and Monday.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 120 AM CDT Tue Aug 4 2026

VFR conditions are likely over the next 24 hours outside the low potential (20-30% chance) for MVFR ceilings and visibilities with isolated showers and thunderstorms this afternoon and evening at CID, DBQ, and MLI. These storms will be associated with a cold front moving through the area, so a wind shift is going to occur throughout the afternoon and evening from southwesterly to northwesterly for CID/DBQ and northeasterly for MLI/BRL. A BKN stratus deck is also expected with this boundary, but ceilings are going to be around 7 kft, comfortably in the VFR category.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.